There are three types of lesions found in the arteries which are associated with atherosclerosis: fatty streaks, fibrous plaques, and complicated plaques. Fatty streaks occur early in life and consist of an accumulation of lipid-filled macrophages and smooth muscle cells (foam cells) and accumulated fibrous tissue on the intima. In general, these fatty streaks appear not to be particularly dangerous in themselves; however, they may be contributory to the formation of fibrous plaques. Fibrous plaques are raised lesions on the intima. These plaques consist of a central core of extracellular lipid and necrotic cell debris and are covered with an overlayment of smooth muscle cells and collagen matrix. This makes the fibrous plaque foci, a place of constricted blood flow in the artery. The fibrous plaque is characteristic of advancing atherosclerotic disease. The complicated plaque is a calcified fibrous plaque and is an area of thrombosis, necrosis, and ulceration. This plaque constricts the blood flow and causes stenosis that can lead to organ insufficiency. The site of a complicated plaque is, also, an area of weakened arterial wall which may fail, causing aneurysm formation and hemorrhaging.
One theory of atherogensis is the reaction-to-injury hypothesis. According to this hypothesis, the lining endothelial cells of the artery are exposed to acute, repeated acute, or chronic injury, which causes the cells to detach from one another, thus exposing the underlying connective tissue bed. This break in the continuous system of endothelium elicits platelet adhesion, aggregation, and the formation of microthrombi. This platelet interaction causes the release of mitogenic factors leading to the proliferation of smooth muscle cells, the production of matrix, and the trapping of lipids from the serum. Although this repairs the immediate break in the system, the disturbance in the blood around the lesion often causes further damage to endothelium in adjacent areas, especially down stream from the initial insult, thus increasing the plaque size. This process continues to build the lesion and leads to constriction of the blood flow and eventual occlusion or failure of the arterial wall.
Today, balloon angioplasty is one of the most common procedures used in treating atherosclerotic plaques, especially for relatively small plaques. It is often preferred over by-pass surgery, in that it is less expensive and is a great deal less traumatic to the patient.
Although angioplasty is very effective at initially opening the occluded artery, this artery often fails to remain open for an extended period of time. Within one year, 30-50% of the arteries opened by angioplastic surgery are occluded in the same or adjacent location as the initial blockage. The process by which this re-occlusion occurs is called restenosis. For reviews covering the morphologic changes and biopathology of restenosis following angioplasty see: Haudenschild, C. C., Am. J. of Med., 94, (Suppl 4A), p. 4A-40S-4A44S (1993) and Waller, B. F., et al. Radiology, 174,(3), p.961-967 (1990).
Currently, there is no treatment for the restenosis of an artery, other than repeating the angioplasty, which may exacerbate the problem, or performing a more extensive procedure such as by-pass surgery.
It has been shown that another benzothiophene, raloxifene (formula I, R.sub.1 is n-piperidenyl, and R.sub.2 and R.sub.3 are hydrogen) is active in experimental models in inhibiting restenosis (see: EP652,003, published May 10, 1995). In experimental models conducted in vivo, raloxifene was administered via a systemic route (oral) demonstrating its beneficial effect at inhibiting restenosis. Additionally, it has now been shown that raloxifene is capable of inhibiting intimal thickening at a local site of angioplasty insult. This result is of great significance in that raloxifene is of a chemical class of compounds known as mixed estrogen agonist/antagonists, or SERMs, selective estrogen receptor modulators. Administration of a compound having a similar profile as that of raloxifene, but at the local site, would be an advantage for the treatment of restenosis induced by angioplastic intervention.
Ideally, it would be desirable to administer such an agent directly into the plaque at the time of angioplasty. This is problematic in that raloxifene is not very soluble in the highly lipophilic matrix found in the atherosclerotic plaque. Additionally, large volumes of solvent would be necessary to dissolve an effective amount of raloxifene which would then have to be delivered via the angioplasty catheter into the atherosclerotic plaque. Both of these raise practical concerns over the use of either raloxifene or its known derivatives from use as locally active agents for preventing restenosis via an angioplasty catheter.
It would be of great benefit if there were an efficient non-surgical treatment for restenosis. It would be of particular benefit if such a treatment could be confined to the immediate locality of the occluding plaque, since this would limit any potential side-effects of the treatment. A treatment such as a drug which could be delivered locally to the plaque site at the time of angioplasty and prevent restenosis at that site would be ideal.
"Post-menopausal syndrome" is a term used to describe various pathological conditions which frequently affect women who have entered into or completed the physiological metamorphosis known as menopause. Although numerous pathologies are contemplated by the use of this term, three major effects of post-menopausal syndrome are the source of the greatest long-term medical concern: osteoporosis, cardiovascular effects such as hyperlipidemia, and estrogen-dependent cancer, particularly breast and uterine cancer.
Osteoporosis describes a group of diseases which arise from diverse etiologies, but which are characterized by the net loss of bone mass per unit volume. The consequence of this loss of bone mass and resulting bone fracture is the failure of the skeleton to provide adequate structural support for the body. One of the most common types of osteoporosis is that associated with menopause. Most women lose from about 20% to about 60% of the bone mass in the trabecular compartment of the bone within 3 to 6 years after the cessation of mensus. This rapid loss is generally associated with an increase of bone resorption and formation. However, the resorptive cycle is more dominant and the result is a net loss of bone mass. Osteoporosis is a common and serious disease among post-menopausal women.
There are an estimated 25 million women in the United States, alone, who are afflicted with this disease. The results of osteoporosis are personally harmful and also account for a large economic loss due its chronicity and the need for extensive and long term support (hospitalization and nursing home care) from the disease sequelae. This is especially true in more elderly patients. Additionally, although osteoporosis is not generally thought of as a life threatening condition, a 20% to 30% mortality rate is related with hip fractures in elderly women. A large percentage of this mortality rate can be directly associated with post-menopausal osteoporosis.
The most vulnerable tissue in the bone to the effects of post-menopausal osteoporosis is the trabecular bone. This tissue is often referred to as spongy or cancellous bone and is particularly concentrated near the ends of the bone (near the joints) and in the vertebrae of the spine. The trabecular tissue is characterized by small osteoid structures which inter-connect with each other, as well as the more solid and dense cortical tissue which makes up the outer surface and central shaft of the bone. This inter-connected network of trabeculae gives lateral support to the outer cortical structure and is critical to the bio-mechanical strength of the overall structure. In post-menopausal osteoporosis, it is, primarily, the net resorption and loss of the trabeculae which leads to the failure and fracture of bone. In light of the loss of the trabeculae in post-menopausal women, it is not surprising that the most common fractures are those associated with bones which are highly dependent on trabecular support, e.g., the vertebrae, the neck of the weight bearing bones such as the femur and the fore-arm. Indeed, hip fracture, collies fractures, and vertebral crush fractures are hallmarks of post-menopausal osteoporosis.
At this time, the only generally accepted method for treatment of post-menopausal osteoporosis is estrogen replacement therapy. Although therapy is generally successful, patient compliance with the therapy is low primarily because estrogen treatment frequently produces undesirable side effects.
Throughout premenopausal time, most women have less incidence of cardiovascular disease than age-matched men. Following menopause, however, the rate of cardiovascular disease in women slowly increases to match the rate seen in men. This loss of protection has been linked to the loss of estrogen and, in particular, to the loss of estrogen's ability to regulate the levels of serum lipids. The nature of estrogen's ability to regulate serum lipids is not well understood, but evidence to date indicates that estrogen can upregulate the low density lipid (LDL) receptors in the liver to remove excess cholesterol. Additionally, estrogen appears to have some effect on the biosynthesis of cholesterol, and other beneficial effects on cardiovascular health.
It has been reported in the literature that post-menopausal women having estrogen replacement therapy have a return of serum lipid levels to concentrations to those of the pre-menopausal state. Thus, estrogen would appear to be a reasonable treatment for this condition. However, the side-effects of estrogen replacement therapy are not acceptable to many women, thus limiting the use of this therapy. An ideal therapy for this condition would be an agent which would regulate the serum lipid level as does estrogen, but would be devoid of the side-effects and risks associated with estrogen therapy.
The third major pathology associated with post-menopausal syndrome is estrogen-dependent breast cancer and, to a lesser extent, estrogen-dependent cancers of other organs, particularly the uterus. Although such neoplasms are not solely limited to a post-menopausal women, they are more prevalent in the older, post-menopausal population. Current chemotherapy of these cancers has relied heavily on the use of anti-estrogen compounds such as, for example, tamoxifen. Although such mixed agonist-antagonists have beneficial effects in the treatment of these cancers, and the estrogenic side-effects are tolerable in acute life-threatening situations, they are not ideal. For example, these agents may have stimulatory effects on certain cancer cell populations in the uterus due to their estrogenic (agonist) properties and they may, therefore, be contraproductive in some cases. A better therapy for the treatment of these cancers would be an agent which is an anti-estrogen compound having negligible or no estrogen agonist properties on reproductive tissues.
In response to the clear need for new pharmaceutical agents which are capable of alleviating the symptoms of, inter alia, post-menopausal syndrome, the present invention provides new benzothiophene compounds, pharmaceutical compositions thereof, and methods of using such compounds for the treatment of post-menopausal syndrome and other estrogen-related pathological conditions such as those mentioned below.
Uterine fibrosis (uterine fibroid disease) is an old and ever present clinical problem which goes under a variety of names, including uterine fibroid disease, uterine hypertrophy, uterine lieomyomata, myometrial hypertrophy, fibrosis uteri, and fibrotic metritis. Essentially, uterine fibrosis is a condition where there is an inappropriate deposition of fibroid tissue on the wall of the uterus.
This condition is a cause of dysmenorrhea and infertility in women. The exact cause of this condition is poorly understood but evidence suggests that it is an inappropriate response of fibroid tissue to estrogen. Such a condition has been produced in rabbits by daily administrations of estrogen for 3 months. In guinea pigs, the condition has been produced by daily administration of estrogen for four months. Further, in rats, estrogen causes similar hypertrophy.
The most common treatment of uterine fibrosis involves surgical procedures both costly and sometimes a source of complications such as the formation of abdominal adhesions and infections. In some patients, initial surgery is only a temporary treatment and the fibroids regrow. In those cases a hysterectomy is performed which effectively ends the fibroids but also the reproductive life of the patient. Also, gonadotropin releasing hormone antagonists may be administered, yet their use is tempered by the fact they can lead to osteoporosis. Thus, there exists a need for new methods for treating uterine fibrosis, and the methods of the present invention satisfy that need.
Endometriosis is a condition of severe dysmenorrhea, which is accompanied by severe pain, bleeding into the endometrial masses or peritoneal cavity and often leads to infertility. The cause of the symptoms of this condition appear to be ectopic endometrial growths which respond inappropriately to normal hormonal control and are located in inappropriate tissues. Because of the inappropriate locations for endometrial growth, the tissue seems to initiate local inflammatory-like responses causing macrophage infiltration and a cascade of events leading to initiation of the painful response. The exact etiology of this disease is not well understood and its treatment by hormonal therapy is diverse, poorly defined, and marked by numerous unwanted and perhaps dangerous side effects.
One of the treatments for this disease is the use of low dose estrogen to suppress endometrial growth through a negative feedback effect on central gonadotropin release and subsequent ovarian production of estrogen; however, it is sometimes necessary to use continuous estrogen to control the symptoms. This use of estrogen can often lead to undesirable side effects and even the risk of endometrial cancer.
Another treatment consists of continuous administration of progestins which induces amenorrhea and by suppressing ovarian estrogen production can cause regressions of the endometrial growths. The use of chronic progestin therapy is often accompanied by the unpleasant CNS side effects of progestins and often leads to infertility due to suppression of ovarian function.
A third treatment consists of the administration of weak androgens, which are effective in controlling the endometriosis; however, they induce severe masculinizing effects. Several of these treatments for endometriosis have also been implicated in causing a mild degree of bone loss with continued therapy. Therefore, new methods of treating endometriosis are desirable.